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Partial Dentures > Clasps and Levers > Flashcards

Clasps and Levers Flashcards

1
Q

three components of a clasp assembly

A
  1. rest
  2. retainer (retention)
  3. bracer
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2
Q

Type I clasp aka

A

suprabulge (above height of contour)

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3
Q

Type II clasp aka

A

infrabulge

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4
Q

Describe type I clasp

  • origin
  • retention
A

Occlusal in origin and FROM MINOR CONNECTOR

CROSSES BULGE (height of contour) and is ONLY RETENTIVE IN THE TERMINAL 1/3

retention can be on either the buccal or the lingual but NEVER BOTH
- so only one undercut per tooth

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5
Q

examples of type I clasps

A
  1. circumferential - “C” clasp
  2. combination - combo
  3. ring
  4. embrasure
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6
Q

retention and material for C (akers) clasp

A

Retention may be buccal OR lingual

Retention may be mesial OR distal

Material may be cast or wrought
- may be on framework or soldered on

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7
Q

material for C clasp

A

Casting = tapered
- stronger and thick and ONE-PIECE CASTING

Wrought wire = round
- wire arm soldered or welded to frame work

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8
Q

what do wrought wire clasps require?

A

requires soldering or welding which requires access to an open proximal surface

  • bulky solder joints
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9
Q

wire claps cannot originate from where?

A

Embrassures

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10
Q

T/F Combo clasps can be used in areas with large cervical convergences and undercuts?

A

TRUE

- clasp we would use here

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11
Q

material to make combo clasp?

A

Cast and wrought wire

  • it is a C with a WIRE RETENTIVE ARM
  • must be soldered or welded to casting
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12
Q

origin of combo clasp

A

EDENTULOUS space

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13
Q

flexibility of combo clasp

A

3 times MORE flexible than cast claps

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14
Q

which is more subject to breakage, combo or cast clasp?

A

Combo

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15
Q

protection in combo clasp?

A

Protects tooth AT ITS OWN EXPENSE

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16
Q

Use of a ring clasp?

A

used on lone -standing MOLARS

used ONLY in non-rotating partials

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17
Q

characteristics of a ring clasp

A
  1. 2 rests
  2. 2 minor connectors
  3. has almost continous contact on the tooth
  4. helps INCREASE BRACING – continuous bracing arm
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18
Q

what are disadvantages to embrasure clasps?

A
  1. lack guide planes
  2. places clasps too close together
  3. may act as an interproximal wedge
  4. may cause occlusal or esthetic problems
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19
Q

what determines a clasp flexibility

A
  1. material
  2. length
  3. thickness
  4. straightness
  5. cross-sectional shape
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20
Q

clasp flexibility: material

A

Cr-Co < Au (gold) < wire

  • wire is most flexible
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21
Q

clasp flexibility: length

A

short < long

short is less flexible
6mm minimum

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22
Q

clasp flexibility: thickness

A

tip should taper

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23
Q

clasp flexibility: staightness

A

bends decrease flexibility

should contain less bends as possible

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24
Q

clasp flexibility: cross - sectional shape

A

flat < round

flat is less flexible than round

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25
Q

shape of cast clasp

A

1/2 round

COMBO = wrought - ROUND

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26
Q

what should the tip of a clasp always be?

A

tapered and should be trimmed and polished to shape after casting

*not paddle shaped

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27
Q

origin and finish of type 1 clasp

A

occlusal in origin –> from minor connector–>crossed bulge –. and retentive last 1/3 of it ends in the undercut

retention can be on the buccal or lingual aspect

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28
Q

in type 1 clasp retention arm called retention arm but in type II what are they called?

A

APPROACH arm (vertical)

Retainer (horizontal)

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29
Q

origin of type II clasp

A

gingival

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30
Q

where does type II clasp come from

A

gingival and FROM MESHWORK (not minor connector like type 1 clasp)

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31
Q

type II clasp location in reference to the bulge

A

stays below the bulge

- so all of it is considered retentive

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32
Q

where is the retention on a type II clasp?

A

ALWAYS ON THE BUCCAL

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33
Q

Examples of type II clasps

A
  1. Bar
  2. T- bar
  3. RPI
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34
Q

when you have an approach arm that means you must have what?

A

an approach arm

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35
Q

describe a bar (roach or J bar) clasp

A

this is a type 2 clasp

retention : DISTO-BUCCAL ONLY

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36
Q

which contacts less tooth surface? C clasp or Bar?

A

Bar

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37
Q

when is bar contraindicated

A

when an approach arm is contraindicated

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38
Q

T- bar clasp description

A

major difference is that the mesial aspect of the retentive part is above the survey line meaning it is NOT RETENTIVE BUT BRACING
- utilized when we do not have enough bracing on the opposite side of the tooth

*retention is still DB only

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39
Q

what does RPI stand for? what type of clasp?

A

R- Rest
P -Proximal plate
I - bar

type II clasp

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40
Q

RPI metal touching teeth?

A

less than a T and less than a bar clasp

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41
Q

retention on RPI

A

mid or mesial buccal only

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42
Q

rest in RPI for pre-molars?

for cuspids?

A

pre-molars on mesio-occlusal

on cuspids = on mesio-lingual

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43
Q

bracing for RPI

A

2 minor connectors only and has least amount of metal when compared to any other clasp

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44
Q

minimum distance for any type 2 clasp?

A

2 mm from the free gingival margin for any undercut

3mm in height before it starts to swing back and join the framework

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45
Q

orientation of the approach arm to the free gingival margin in an RPI?

A

the approach arm is perpendicular to the free gingival margin

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46
Q

where you can use approach arms?

A

Can:
tooth = tissue (ideally) (.01 undercut) and tissue is 3mm below)

TISSUE UNDERCUT below 3mm - so goes into undercut after you alwready have the 3mm you need

ledge - okay again if you have 3mm and then it ledges out (we can contour the approach arm to the ledge)

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47
Q

where/ when are approach arms contra-indicated?

A
  1. tissue undercut above 3mm (do not have the 3mm distance we need) tissue immediately goes into undercut
  2. SEVERE TILT - if we try to adjust tooth - prepping too much
    - way too much space between arm and tooth
48
Q

implication of a space between tissue and approach arm?

A

it will become a food trap and cause lip irritation

49
Q

amount of tissue that needs to be surveyed for a type II clasp?

A

3 mm

50
Q

how to reduce a tissue ndercut?

A

tail down A/P tilt or laterally tilting it away

enamoloplasty

51
Q

five incorrect uses for aproach arms?

A
  1. double arms
  2. skipping of teeth
  3. lingual or palatal
  4. reverse or distal (not going to swing an approach arm from an anterior tooth back)
  5. molars (for same reasons) – buccal shelf and zygomatic arch are there
    * these are saying you do NOT USE THEM HERE
52
Q

why would approach arm be contraindicated in molars?

A

because of location of buccal shelf and zygomatic arch

53
Q

bracing aka

A

reciprocal

54
Q

if she says ‘what is reciprocal’ she means what?

A

what is bracing

55
Q

effect of pushing a fixed object

A

it will TIP unless something opposes it

56
Q

three types of bracers

A
  1. bracing ARMS
  2. bracing BLANKETS (CONGULUM REST)
  3. bracing MINOR CONNECTORS
57
Q

cingulum rest can also be referred to as what

A

blanket

58
Q

advantage of using 2 minor connectors with a type 2 clasp?

A

least amount of metal touches the teeth from the lingual aspect

59
Q

if there is a C clasp of canine/ cuspid what is the bracer?

A

Lingual BLANKET – but ONLY IN A NON-ROTATING PARTIAL

60
Q

when do you use an arm for bracing and where

A

Molar or pre-molar only on buccal or lingual

61
Q

when do you use 2 minor connectors and where

A

lingual of pre-molar or cuspid ONLY for type two claps

62
Q

why can you not use 2 minor connectors on molars?

A

molars are TOO WIDE to be braced by 2 minor connectors

63
Q

what type of bracing is used on canines of non-rotating partials?

A

BLANKET

64
Q

major purpose of bracer

A

neutralize the effect of the retentive tip (so opposite of the retention aspect of clasp)

65
Q

location of a bracer

A

must be MORE THAN 180 degrees from retentive tip
**directly opposite from the retainer
must be viewed from the OCCLUSAL and PROXIMAL

  • At or slightly above the survey line because the retainer is below the survery line (hence the retention component of retainer)
66
Q

Occlusal forces come from what?

A

rests

67
Q

Lateral forces come from what?

A

clasps

68
Q

clasps are placed where? why?

A

placed as gingivally as possible to reduce rotational or tipping forces

69
Q

how do you lower survey line?

A

disk non-parallel to the path

70
Q

two types of retentive undercuts

A
  1. bilateral

2. diametric opposition

71
Q

bilateral opposition undercut location

A

all undercuts are on buccal or all undercuts are on the lingual

72
Q

diametric opposition

A

there are undercuts on the lingual and on the buccal within same arch (maxilla or mandible)

73
Q

ideal location of ubndercuts

A

all (bilateral opposition) on the buccal aspect so all stress on the framework is directed outwards

74
Q

if all undercuts on lingual implication?

A

the stress on the frame is all directed inwards

75
Q

if have B + L mix of undercuts?

A

stress on framework is directed sideways

76
Q

mandibular molars typically tilt which way?

A

lingually

77
Q

implication of a longer edentoulous space?

A

greater the potential of a lever action on the abutment teeth

78
Q

definition of class I lever

A

the FULCRUM is placed BETWEEN the effort and the load

most common lever configuration

79
Q

movement of load in effort in a class I lever

A

the movement of the load is in the OPPOSITE direction of the movement of the effort

80
Q

Class 2 lever defintion

A

has the LOAD BETWEEN the effort and the fulcrum

81
Q

movement of load and effort in class 2 lever

A

the movement of the load is in the SAME DIRECTION as that of the effort

82
Q

location of fulcrum determines what

A

the lever

83
Q

during rotation clasps act as?

A

Levers

84
Q

the rest determines what for levers?

A

the CLASS of lever

85
Q

implication of a longer lever arm?

A

more torque on abutment tooth – easier to dislodge (not good)

86
Q

rest seat on the distal? implication in terms of levers?

A

1st class

87
Q

rest seat on the mesial? implication in terms of levers?

A

2nd class lever

88
Q

fulcrum is?

A

the rest

89
Q

effort is the?

A

biting

90
Q

resistance is the?

A

tooth

91
Q

clasp tip movement in a 2nd class lever?

A

down and away from effort (biting)

92
Q

clasp tip movement in a 1st class lever? implication?

A

up
- bite down and clasp tip moves up into the undercut

CAN EXTRACT TEETH

93
Q

a rest closest to the rotation is what type lever?

A

class 1 lever

94
Q

rest away from the axis of rotation is what type of lever?

A

class 2 lever

95
Q

if have two rests on the teeth what class lever?

A

THE REST CLOSEST TO THE ROTATION = THE LEVER

you classify lever based on which one is closest to the axis of rotation so could still be class I

96
Q

Rest on cuspid in a rotating partial?

A

MESIAL LINGUAL

cingulum/ blanket would include distal and would create a class 1 lever which we do not want

97
Q

movement of a non- rotating partial?

A

up and down

do NOT act as levers

98
Q

movement of a rotating partial?

A

move anterio-posterior

act as levers

99
Q

ideal design for RPI clasp

A

short occlusal rest, short distal guide plane (occlusal 1/3) and mesial shifted I bar

100
Q

biting force

A

36 psi

101
Q

non rotating partials look like?

A

all edentulous spaces have TEETH AT EITHER END

102
Q

all rotating partials have?

A

at least one edentulous space has soft tissue (no teeth) at one end

AKA distal extension

103
Q

in non rotating partials describe what happens to the clasp in terms of active or passive?

A

when in place - passive

when lifted out of place = active (crosses survey line)

then becomes passive as it is past above survey line

then goes active to seat again

then once seated = becomes passive again

104
Q

first and second choice of clasp for non-rotating partials?

A
  1. C clasp (simplest design)

2. any - b/c all non rotating alike

105
Q

what happens if clasp tip is mesial to the rest?

A

the lever changes to a class I

so dont go past the mesial line angle

on cuspids and pre molars always stay mid buccal or just slightly mesial to this

106
Q

only way an RPA can protect a tooth?

A

if used with a class 2 lever

107
Q

order of clasp choice in rotating partial?

A
  1. RPI
  2. RPA COMBO
  3. Bar w/ 2nd class lever
  4. RPA cast
108
Q

cast contact vs wire contact

A

cast –> surface contact

wire –> point contact

109
Q

if teeth are week how do you design?

A

treat as a DE with RPI

110
Q

if bone is week how do you treat?

A

treat as DE with combo

111
Q

implication of having a lingual bracing arm with class i lever

A

when lift up the arm will torque the tooth because it goes into survey line

112
Q

if use two minor connectors for bracing how does this help?

A

now there are two minor connectors and they rotate around the tooth

bite down – rest goes up and other slips into the gingival 1/3

lift up – guide plane and rest engage then other part will slide up

no metal on the lingual portion of the tooth

113
Q

RPA combo location of rest and tip

A

MO rest

MB tip

114
Q

RPI rest and tip location

A

MO rest

Mid B tip

115
Q

Bar rest and tip location

A

MO rest

DB tip

116
Q

RPA c rest and tip location

A

MO rest

MB tip

Partial Dentures (9 decks)

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